וַיִּקְרַ֨ע יְהוֹשֻׁ֜עַ שִׂמְלֹתָ֗יו וַיִּפֹּל֩ עַל־פָּנָ֨יו אַ֜רְצָה לִפְנֵ֨י אֲר֤וֹן יְהוָה֙ עַד־הָעֶ֔רֶב ה֖וּא וְזִקְנֵ֣י יִשְׂרָאֵ֑ל וַיַּעֲל֥וּ עָפָ֖ר עַל־רֹאשָֽׁם׃
At pinunit ni Josue ang kanyang mga damit, at nagpatirapa siya sa lupa sa harap ng kaban ng Walang-Hanggan hanggang sa gabi, siya at ang mga matanda ng Israel; at naglagay sila ng alabok sa kanilang mga ulo.
Ibn Ezra
the hand of the witnesses that is, the hand of every one of the witnesses. Compare, “the heart of the people melted” [Joshua 7: 5], and many similar instances.
Or HaChaim
The difficulty with this approach is that G'd should have told Moses this as soon as the calf had emerged and the people had said: "these are your gods Israel, etc." Moses should have lost some of his spiritual stature the moment the people had become guilty of idol worship. We must assume that there was a good reason for G'd to delay informing Moses about the sin his people had committed. The Talmud Sanhedrin 43 raises the question why G'd did not inform Joshua of Achan's theft of valuables from the city of Jericho before the defeat of the Israelites at the hands of the people of Ai which prompted Joshua to ask G'd why they had suffered such a humiliating defeat (Joshua 7,6). The Talmud answers that G'd did not want to become known as an "informer," a "snitcher." If that argument were applicable here, G'd should not have told Moses about the people's sin until the latter had found out by himself a few hours later. After all, Moses' time on the Mountain was just about completed. Actually, the situation of Achan and the sin of the golden calf cannot be compared. Achan's sin was unknown except to a few people who kept it as their secret. The Jewish people's dancing around the golden calf and offering sacrifices to it was already public knowledge and Moses would have found out about it within hours even if G'd had not told him. Nonetheless, seeing G'd is the epitome of piety why did He tell Moses before the latter commenced his descent?
Redeeming Relevance; Deuteronomy
Another way to understand falling on the face is as an expression of mourning. For instance, when Yehoshua falls on his face after being informed of the collective punishment that came as a result of Achan’s violating the prohibition against looting, it is a sign of anguish akin to mourning (Yehoshua 7:6). Given that sitting on the ground is clearly associated with mourning, it is not unreasonable to say falling on one’s face to the ground can express this as well. At the same time, in light of Bereshit 17:7, it is clearly not always the case. Hence the only question would be whether it is a sign of mourning here. It is not unreasonable to understand it this way with regard to Moshe as well,18Ramban, Abarbanel on Bemidbar 14:5; Da’at Mikra, on Yehoshua 7:6. for there is certainly what to mourn. Yet the Talmud (Taanit 14b) wonders why Moshe responds by falling on his face; why does he not tear his clothes, like Yehoshua and Calev? Additionally, given that Moshe’s action was “in front of the whole community of the congregation of the children of Israel,” why was there no popular reaction to it? If Moshe was trying to censure them with his public mourning, why did they just let it go? Why did they not rebel further or, alternatively, acquiesce and surrender to Moshe’s protest?